Phosphonitrile compositions and methods



United States Patent 3,418,366 PHOSPHONITRILE COMPOSITIONS AND METHODSHarry H. Sisler, Gainesville, Fla., assignor to W. R. Grace & 'Co., NewYork, N.Y., a corporation of Connecticut N0 Drawing. Continuation-impartof applications Ser. No. 154,827, Ser. No. 154,828, Nov. 24, 1961, andSer. No. 426,680, Jan. 19, 1965. This aplication July 1, 1966, Ser. No.567,798

Claims. (Cl. 260551) ABSTRACT OF THE DISCLOSURE Organo substitutedphosphonitrilic compounds are prepared by reacting a disubstitutedmonochlorophosphine with chloramine and ammonia or an equivalentthereof. The phosphonitrilic compounds find utility in the preparationof organic substituted phosphonitrilic polymers which possess hightemperature resistant properties.

This application is a continuation-in-part of m application 426,680,filed Jan. 19, 1965, now abandoned, and applications, Ser. No. 154,827and 154,828, filed Nov. 24, 1961, now abandoned.

The present invention relates to organic substituted phosphonitriliccompounds, and more specifically to novel phosphonitrilic polymerintermediates and polymers as well as to methods for their preparation.

In recent years considerable interest has been expressed in thedevelopment of inorganic polymers having polymeric skeletons orbackbones which do not contain carbon atoms. For several applications,particularly hightemperature use, inorganic polymers often exhibitbetter stability and strength characteristics than their carbon backbonecounterparts. Some of the more promising inorganic polymers have beenphosphonitrilic polymers which possess polymeric structures composed ofrepeating phosphonitrilic units. A general formula (=--R P=N-) wherein Ris often a hydrocarbon radical and n represents a number of repeatingphosphonitrilic units is often used to illustrate these compounds.

To date, the number of phosphonitrilic polymers available is extremelylimited. Furthermore, the presently known methods for preparingphosphonitrilic polymers and their monomeric precursors are extremelytedious and expensive.

It is therefore an object of the present invention to provide a novelclass or organic substituted phosphonitrilic polymers and polymerintermediates.

It is another object to provide a method by which phosphonitrilicpolymers and polymer intermediates may be conveniently and economicallyprepared.

These and still further objects of the present invention will becomereadily apparent to one skilled in the art from the following detaileddescription and specific examples.

In general, the present invention contemplates the following novelembodiments:

(1) Novel polymer intermediates having the formulae:

wherein R represents lower alkyl and aryl, and

wherein R represents lower alkyl, and

( R1P=I|\ll-PR1 wherein R=lower alkyl and aryl (II) A novel method forpreparing compounds of the formulae:

wherein R represents lower alkyl and aryl, which involves reacting adisubstituted monochloro phosphine with chloramine and ammonia, or acompound which for the purposes of the reaction is formally equivalentto chloramine and ammonia, such as hydrazine, hydrazinemonohydrochloride (hydrazinimum chloride), and bydrazinedihydrochloride. (III) A novel method for preparing linear polymershaving the formula:

{-R P=N) wherein R represents lower alkyl and n has a value greater than2 which comprises heating polymer intermediates having the formulae:

and

R P=NPR;

C1 NH wherein R represents lower alkyl to a temperature in excess of 25C. to about 300 C. More specifically, I have found that the above novelphosphonitrilic processes and products may be carried out and preparedin accordance with the detailed procedures and examples set for in thefollowing:

POLYMER INTERMEDIATES AND THE PREPARA- TION THEREOF As indicated above,the novel phosphonitrilic polymer intermediates of the present inventionpossess the formulae:

wherein in (I) and (III) R represents alkyl having from about 1 to 20carbon atoms and aryl, such as phenyl, alkylphenyl and halophenyl and inFormula II R represents alkyl having 1 to 20 carbon atoms.

Compounds (I), (II) and (III) (wherein in compound (II), in addition toalkyl, R may represent aryl) are prepared by reacting an appropriatedisubstituted monochloro phosphine with chloramine and ammonia or acompound, which, for the purposes of the present invention, is theequivalent of chloramine and ammonia, such as hydrazine, hydrazinemonohydrochloride and hydrazine dihydrochloride. Typical reactions whichoccur are summarized in the following equations:

(1) Chloramine-ammonia 3 (4) Hydrazine dihydrochloride In the abovereactions the chloramine and hydrazine reactants are shown as beingnon-substituted. It is contemplated, however, that in the case ofhydrazinium chlorides, hydrazinium chlorides having one or more hydrogenatoms on one nitrogen substituted, particularly the alkyl substitutedmembers having alkyl substitutents ranging from 1 to about 20 carbonatoms, may be used.

To obtain compounds (I) and (11) above, the disubstituted halophosphineis reacted with the chloramineammonia mixture (or equivalent thereto)preferably in the presence of an inert solvent. The ratio of thereactants is not, particularly critical. However, to obtain optimumyields of the desired products, it is preferred that a stoichiometricexcess of chloramine and ammonia (or equivalent) be used. When achloramine-ammonia mixture is used as a preferred embodiment of thepresent invention, the chloramine-ammonia mixture may be convenientlyproduced in accordance with the teachings of U.S. Patent 2,837,409 to H.Sisler. This patent describes a method for preparing chloramine whichcomprises reacting anhydrous chlorine with an excess of anhydrousammonia in the gaseous phase, and removing by filtration the ammoniumchloride produced in the reaction. The molar ratio of ammonia tochlorine is maintained at greater than about 2 to 1 to prevent undesiredside reactions from occurring.

In the present reactions mixtures of compounds (I), (II) and (III) areobtained as well as certain amounts of polymeric products. However, tofavor the formation of a given intermediate certain generalizations maybe made as to preferred reaction conditions.

In the event it is desired to obtain a predominance of compound (I) inthe present reaction, lower temperatures ranging from about to about 150C. are used. At these temperatures, from about 0 to about 60 minutes arerequired to obtain substantial yields of product.

On the other hand, if it is desired to obtain a predominance of compound(II) or (III) reaction temperature ranges from about 150 to about 300 C.and substantially the same reaction times are used.

The present reaction is preferably conducted in the presence of inertorganic solvents such as saturated and unsaturated hydrocarbons havingfrom about to 12 carbon atoms and a boiling point ranging anywhere fromabout 50 to 200 C. Halogenated hydrocarbons falling within this boilingrange may also be advantageously used. Typical examples of inertsolvents which may be used in the present reaction aretetrachloroethane, benzene, pentane, heptane, chlorobenzene andcyclohexane.

Subsequent to the reaction compounds (I), (II) and (HI) are recoveredfrom the reaction mixture by standard extraction and fractionalcrystallization techniques.

NOVEL LINEAR ALKYL SUBSTITUTED PHOS- PHONITRILIC POLYMERS ANDPREPARATION THEREOF The linear phosphonitrilic polymers contemplatedherein possess the general repeating structural unit: (IV) (-R P=N-lwherein R is alkyl having 1 to 20 carbon atoms and n has a value greaterthan 2 and preferably from about to about 10,000. These polymers areprepared by heating intermediate compounds (I), (II) and (III) (whereinR is alkyl) to a temperature in excess of about 100 C. up to about 250C.

The polymerization reaction which occurs using intermediate (I) issummarized by the following equation:

it 2] nNH cl Polymers (IV) above possess from about 10 to about 10,000repeating units which results in molecular weights ranging from about950 to about 6 10 depending on the molecular weight of R. These polymershave melting points which range from about to about 250 C. The polymersare generally described as non-volatile, glassy linear products whichare soluble in benzene, chloroform but insoluble in acetone and water.

These polymers possess valuable utility in high temperature applicationsin that they remain stable for extended periods of time at temperaturesin excess of about 250 C.

The present polymers are prepared by heating intermediates (I), (II) and(III) at temperatures in excess of about 200 C. for times ranging fromabout 1 to about 48 hours. Preferably the heating is carried out undervacuum. The residue which remains subsequent to the heating under vacuummay be dissolved in benzene at temperatures ranging from 30-35 C. andsubsequently. be precipitated at lower temperatures on the order of 25C. Infra-red analysis and quantitative elemental analysis sustains thestructure (IV) indicated above.

In a preferred embodiment, the heating or compound (I) to producedlinear polymer (IV) is conducted in the presence of up to about 30% byweight of ammonium chloride (NH Cl). The presence of the ammoniumchloride enhances the formation of the desired polymer.

PREPARATION OF CYCLIC PHOSPHONITRILES The present method for preparingcyclic phosphonitriles of the formula:

wherein R may represent phenyl and alkyl having 1 to 20 carbon atomsinvolves heating compound (I), wherein R represents alkyl and aryl andcompounds (II) and (III), wherein R represents aryl and alkyl, to atemperature in excess of from about 25 C. for about 1 to 48 hours.Typical reactions which occur are as follows:

Furthermore, cyclic phosphonitrilics (V) may be prepared directly fromthe reaction mixture used to prepare intermediates (1), (II), and (111)without any intermediate separation of (I), (II) or (III). In such casethe reaction mixture is merely held at a temperature in excess of 25 C.for this required time. Typical overall reactions which occur as asfollows:

In a preferred procedure for preparing cyclic polymers (V) the heatingof (I), (II) and (III) is conducted in the absence of ammonium chloride.By conducting the reaction under vacuum ammonium chloride is sublimedfrom the reaction mixture and the desired condition is achieved. Vacuumson the order of 0.5 mm. of Hg produce a satisfactory result.

Having described the basic aspects of the present invention, thefollowing examples are given to illustrate embodiments thereof.

Example I Dimethyl chlorophosphine (0.0206 mole) was dissolved in 50milliliters of dried benzene and exposed to the affluent gases of achloramine generator which produced about 0.0018 mole of chloramine and0.022 mole of ammonia per minute. An ice bath was used to cool themixture at the beginning of the chloramine ammonia addition. A

, powder by addition of petroleum ether. The melting point of thematerial was 195-200 C. The yield was 1.60 grams which represented a 60%yield based on dimethyl chlorophosphine used.

Elemental analysis determined the following values: C, 18.44; H, 7.84;P, 23.82; N, 22.00; Cl, 28.1. Calculated for [(CH P(NH ]C1: C, 18.69; H,7.84; P, 24.10; N, 21.79; Cl, 27.58.

Example 11 A 1.2 gram sample of dimethyl diaminophosphonium chlorideprepared by the process similar to that set forth in Example I wasplaced in a vacuum sublimation apparatus mixed with 0.13 gram of NH Cland heated under a vacuum of about 0.20 millimeter of mercury attemperature of 200-220 C. This temperature pressure was maintained forabout 3 days. At the end of this period a white sublimate had formed ona coldfinger within the apparatus and a glassy residue remained in thepot. This residue was determined to be a linear phosphonitrilic polymer.The yield was 0.22 gram which represented a 32% yield based on dimethyldiamino phosphonium chloride used.

The crude phosphonitrilic polymer which comprised repeating monomericunits [(CH PN)] as obtained from the pot had a dark glassy appearance.The polymer is soluble in benzene at a temperature of 3035 C. andprecipitates as a fiocculent when the benzene solution is cooled to 25C. The polymer was soluble in chloroform and insoluble in acetone andwater. Evaporation of the benzene solution of the polymer yields a lightbrown powder which melts at 137-141 C. The average molecular weight wasdetermined at 7640, as determined in a benzene solution with a Mecrolabvapor pressure asmometer.

The analyzed composition was: C, 31.81; H, 8.16, N, 18.79; P, 41.14.Calculated for CH PN: C, 32.01; H. 8.06; N, 18.66; P, 41.28. Theinfra-red spectrum of the polymer shows strong peaks at 690 cmf 725-763,850- 930, 950-970, 1100-1390, 1420-2000, 2950-3000.

Example 111 11.9 grams of diphenyl chlorophosphine and 7.0 grams oftriethyl hydrazinium chloride were heated together in absence of solventat a temperature of l30-140 C. for 40 hours. Hydrogen chloride gasevolved during this period. The reaction mixture was digested inbenzene, filtered and the filter was cooled. A white precipitate formedwhich was identified as [(C H PN)] by melting point and infra-redspectrum. The material was obtained in a yield of 41% of theory based onthe diphenyl chlorophosphine used. The benzene insoluble portion wasidentified as 2 5) a 1 Example IV 1.7 grams (0.008 mole) of diphenylmonochlorophosphine and 1.1 gram (0.01 mole) of hydrazinedihydrochloride having the formula (NI-l NH )Cl was heated in ananhydrous system at atmospheric pressure for 48 hours at a temperatureof 245 to 250 C. During the initial period of the reaction considerablehydrogen chloride was involved. At the end of the 48 hour period thepressure was reduced to 0.5 mm. Hg., for 4 hours to sublime ammoniumchloride. The residue melted at 310-312 C. and weighted 0.6 gram whichrepresented 40% yield based on the amount of diphenyl chlorophosphineused. This product was recrystallized from benzene and was subsequentlyfound to posses a melting point of 318.5 to

319.5 C. When admixed with an authentic sample of phosphonitriletetramer the substance melted at 318.5 to 319.5 C. Infra-red spectra ofproduct and of the authentic tetramer sample were identical.

Example V A mixture of 4.25 g. (0.02 mole) of diphenyl chlorophosphinewas admixed with 2.7 g. (0.04 mole) of hydrazine monohydrochloride andheated at a temperature of 250 C. for about 48 hours. The reactionmixture was then subjected to a reduced pressure of 0.5 mm. Hg. for 3hours to sublime ammonium chloride which formed during the reaction. Thereaction product was subjected to multiple crystallizations frombenzene. These crystallizations yielded 1.1 g. of diphenylphosphonitriletetramer (28% yield) and 0.5 g. of diphenylphosphonitrile trimer (13%yield).

Example VI A solution of 22.1 g. (0.1 mole) of diphenyl chlorophosphinein 50 ml. of sym. tetrachloroethane was added dropwise with stirring toa refluxing suspension of 7.0 g. (0.1 mole) of hydrazinemonohydrochloride in ml. of sym. tetrachloroethane. After stirring atreflux temperature (146 C.) for 4.5 hours the solids in the reactionmixture were filtered off and washed with benzene and ethyl ether. Thesolids were further extracted with boiling benzene which left a residueof ammonium chloride. White granular crystals (melting point 222-225 C.)weighing 3.2 g. separated from the combined solutions which held theproducts. Repeated crystallizations from benzene raised the meltingpoint to 229-230 C. The infrared spectrum and melting point of a mixtureof the prodnot with an authentic sample of diphenyl phosphonitriletrimer confirmed the fact that the product was diphenyl phosphonitriletrimer.

Evaporation of the filtrate obtained in the previous crystallizationsyielded another 7.5 grams of trimer and 1.0 g. of a compound having theformula:

Pyrolysis of this compounded at near its melting point at 268 C. yielded0.8 g. of diphenyl phosphonitrile trimer and tetramer in a ratio ofabout 5:1. Each of these products Was identified by its infra-redspectrum, melting point, and mixed melting point with authentic sampleof trimer and tetramer.

Example VII 5.74 grams of diphenylchlorophosphine (0.026 mole) wasdissolved in milliliters of tetrachloroethane (B.P. l44.6 C.). A mixtureof ammonia and chloramine from from a chloramine generator was bubbledinto the above solution for 20 minutes at room temperature. During thechloramine-ammonia addition, the temperature of the reaction mixturerose to the reflux temperature of the solvent. Subsequent to thechloramine-ammonia addition the precipitated reaction product wasfiltered and washed with tetrachloroethane. This crude product was foundto weigh about 8 grams. This was dissolved in about 200 milliliters ofbenzene, boiled for a few minutes and filtered. From the filtrate about1.08 grams of crystals which melted at 317 to 318 C. was isolated. Thismaterial was found to be essentially diphenylphosphonitrile tetramer andrepresented a 21% yield. From the same benzene solution, 0.30 gram ofdiphenylphosphonitrile trimer having a melting point of 231 C.separated. The yield of trimer was about 6.0%.

Example VIH tetrachloroethane. The reaction vessel was heated externallyby an infra-red lamp, which when combined with the best of reactionraised the temperature of the reaction mixture to reflux. After a fewminutes the temperature was allowed to drop to the range of 80 to 90 C.At the end of the reaction the solid reaction products were filteredunder an atmosphere of dry nitrogen and washed with 2-l00 ml. portionsof tetrachloroethane. The combined filtrate and washings were evaporatedat reduced pressure yielding a light brown colored solid (4.1 gms.)(melting point 236 to 237 C.). Recrystallization from methanol raisedthe melting point to 240 C. and the product was identified as havingformula (referred to hereinafter as X) reaction was extracted with 2-100ml. portions of benzene. Reduction of the volume of the benzene extractthrough evaporation yielded 1.6 gms. of a crystalline solid (meltingpoint 114 C.). This solid was identified as a tetrachloroethane adductof diphenylphosphinitrile trimer having the formula:

On standing in the atmosphere or on being pumped in vacuum this adductis converted quantitatively to diphenyl phosphinitrile trimer.

3.12 gms. of compound (X) was heated at 260 to 265 C. for a period of 3hours and the resulting dark colored residue treated with 150 mls. ofboiling benzene. Reduction of the volume of the resulting benzenesolution lead to the formation of 1.52 gms. of a crystalline solidmelting at 315 to 316 C. which was identified as diphenylphosphonitriletetramer. This corresponds to a 55.4% yield. Further conversion of themother liquor yielded a second crop of crystals (0.8 g.) which was alsoidentified as diphenylphosphonitrile tetramer. Thus the pyrolysis ofcompound (X) at 260265 C. for 3 hours produces thediphenylphosphonitrile trimer and tetramer in a gross yield of 85%.

Example IX Repetition of the procedure set forth in Example VIII yieldedthe following results which are tabulated below:

Diethylchlorophosphine (0.0154 mole) was dissolved in 50 ml. of benzeneand exposed to the efiluent gases of the chloramine generator for 1215minutes (0.016 mole of NH Cl) requires approximately 9.6 minutes. At thestart of the chloramine-ammonia addition the solution grew warm and wascooled with an ice bath. A white precipitate formed immediately. At thecompletion of the reaction the benzene was removed by filtration and thesolids were extracted with two 20 ml. portions of benzene. Uponevaporation of the benzene solution and washings, 2.41 g. of crudematerial melting at 45-50 C. was obtained. After purification byrepeated recrystallizations from benzene the melting point was raised to58-61 C.

Analysis.Found: C, 37.29; H, 9.35; P, 23.68; C1, 13.48. Calculated forC, 37.00; H, 9.31; P, 23.85; Cl, 13.65. Yield: 1.51 g. (75% of theory).

This material is water soluble and highly hygroscopic.

Example XI The solids remaining in the reaction flask after the benzeneextraction of Example X were extracted with two 25 ml. portions ofabsolute ethanol. The solution was concentrated to about half theoriginal volume by evaporation, and ammonium chloride was precipitatedby the addition of petroleum ether. The solution was filtered andfurther concentrated. When the'formation of crystals was observed in thesaturated solution, it was treated with acetone to quantitativelyprecipitate a white solid. Upon filtration and drying, the materialmelted at 103 C. Recrystallization from alcohol yield the pure product,M.P. 106-108.5 C.

Analysis.Found: C, 30.33; H, 8.99; P, 19.51; N, 17.73; Cl, 22.86.Calculated for [(C H P(NH ]Cl: C, 30.08; H, 9.01; P, 19.78; N, 17.89;Cl, 22.64. Yield: 0.46 g. (19% of theory).

This material is water soluble and highly hygroscopic.

Example XII Di-n-butylchlorophosphine (0.0102 mole) was dis solved in 50ml. of dry benzene and exposed to the efiluent gases of the chloraminegenerator for 12-15 minutes. A white precipitate formed immediately. Anice bath was used to cool the mixture at the beginning of thechloramine-ammonia addition. At the completion of the reaction thebenzene was removed by filtration and the solids were washed with two 20ml. portions of dry benzene and filtered. The solids were then extractedwith two 25 ml. portions of chloroform. The chloroform solution wasremoved from the insoluble ammonium chloride by filtration. Petroleumether was added to the chloroform solution and a white, flocculentprecipitate formed and was recovered by filtration. After purificationby recrystallization from chloroform and drying in vacuum, the materialmelted at 113.5 C.

Analysis.Found: C, 45.14; H, 10.45; P, 13.14. Calculated for [(C4H P('NH]Cl: C, 45.17; H, 10.43; P, 14.56; N, 13.17. Yield: 0.53 g. (25% oftheory).

The material is water soluble and highly hygroscopic.

Example XIII Upon evaporation of the benzene solution obtained inExample XII an unidentified viscous oil was isolated. Most of thesolvent was removed freezing the mixture in a Dry Ice-acetone bath andallowing it to thaw slowly under high vacuum. By repeating thisprocedure most of the solvent was removed and a wax-like product wasrecovered. The infrared spectrum of this wax is quite similar to that of[(C H P(NH )-N=P(NH (C I-I ]Cl. The analytical data are compared in thetable below with values calculated for the formulation 0.89 gram of thiswax was recovered.

Percent Percent Percent Percent Percent O H P N 01 wherein R and R arealkyl groups having 1 to 4 carbon atoms. 1

2. The compound dimethyl diamino phosphonium chloride.

9 3. The compound diethyl diamino phosphonium chloride.

4. The compound dibutyl 'diamino phosphonium chloride.

5. A method for preparing a compound selected from the group consistingof z 2)z L [R P (NH =NP ('NH R ]Cl RzP=NP-Rg (:1 NH

{R P=N-) wherein R is selected from the group consisting of an and alkylgroup having 1 to 4 carbon atoms and n has a 15 value of 3 or 4 whichcomprises reacting in the presence of an inert solvent, under anhydrousconditions, a disubstituted monochlorophosphine having the formula RPCl, wherein R represents alkyl groups having 1 to 4 carbon atoms andphenyl groups, with a member selected from the group consisting ofchloramine-ammonia mixture, hydrazine triethyl and unsubstitutedhydrazinium chloride and hydrazine diyhydrochloride. 6. The method ofclaim 5 wherein the reaction is conducted at a temperature ranging fromabout 30 to 400 C.

7. The method of claim 5 wherein said heating is continued untilammonium chloride ceases to be produced in the reaction mixture.

8. A method for preparing linear polymer possessing the repeatingstructural unit wherein R represents lower alkyl and n has a valuegreater than 2, which comprises heating References Cited UNITED STATESPATENTS 3/1940 Lipkin 260-2 2/ 1965 Liu et al. 2602 OTHER REFERENCESBenzman et al.: Chemistry and Industry, pp. 839-840 (June 25, '1960).

Sisler et al.: Inorganic Chemistry, vol. I, No. I, pp. 84- 88 (February1962).

HENRY R. JILES, Primary Examiner.

H. I. MOATZ, Assistant Examiner.

U.S. Cl. X.R. 2602

